1. Field of the Invention
The present invention relates to a base station antenna, and more particularly to a base station antenna supporting multiple antenna schemes.
2. Description of the Related Art
Development of mobile communication technology is followed by expectations that, even before the 3G (3rd Generation) networks are saturated, 4G (4th Generation) networks will be constructed widely. One of international standards representing the 4G networks, i.e. Mobile WiMAX or LTE (Long Term Evolution) communication scheme, applies various technologies to increase the transmission rate per frequency band, i.e. capacity (bps/Hz), and, for the purpose of the most effective capacity increase, applies multiple antenna technology referred to as MIMO (Multi-Input Multi-Output).
The essentials of multiple antenna technology for base station antennas are based on baseband signal processing technology. However, the degree of capacity increase, when multiple antennas are used, heavily depends on the antenna configuration. The reason is as follows: the multiple antenna technology makes active use of a number of multi-path fading and, at the same time, seeks to remove interference signals from other subscribers. This means that, even if the antenna configuration is the same, the degree of capacity increase varies depending on the wave propagation environment and subscriber distribution of the area covered by the base station. Therefore, international standards do not include particulars regarding the antenna configuration and allow free installation of antennas, based on field situations, to maximize the capacity.
However, conventional multiple antenna technologies have a limitation in that, since the antenna beam is fixed, capacity increase can not be expected, once installation is completed, in adaptive response to the wave propagation environment and subscriber distribution, but solely by using baseband signal processing technology. If necessary, the operator may, for example, climb the tower and modify the antennas themselves or their configuration. However, this approach requires a large amount of time and budget for modification and optimization and cannot easily handle situations having time-varying wave propagation environment and subscriber distribution. In summary, conventional antenna technologies cannot reflect the condition of communication environment in real time to perform load balancing, and provide no method for directing the antenna beam towards a hotspot area at a remote location.